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Our Current Projects
Project Four
Australian Children of
Alcoholic Female Twins |
| This project is a
continuation of work that seeks to characterize genetic and family
environmental influences in the development and course of alcoholism
and comorbid psychopathology, with a focus on outcomes in adolescent
offspring (aged 13-21) of Australian alcoholic and control mothers and
their twin sisters. Project 4
represents a novel and rigorous investigation of critical, yet still
unresolved, issues regarding the nature of alcoholism. Most
importantly, we are utilizing a children-of-twins (COT) method embedded
within a
longitudinal design to learn more about GE correlations and
interactions that characterize the environmental consequences (and
genetic correlates) of maternal alcoholism, and ultimately their role
in the development of alcoholism in the offspring generation. Of
particular importance, this prospective study will (i) provide
confirmation in a younger age-group (7-11 year-olds) of associations
between parental alcoholism and offspring ADHD, ODD and CD that have
emerged from our analyses of adolescents and young adults; and (ii)
provide strong evidence regarding
causal relations and the persistence of effects into the older
adolescent and young adult years; and will help us identify young adult
characteristics that qualify the impact of early stage influences and
that are predictive of different alcohol use trajectories (pathways)
throughout the young adult years. It is anticipated that findings will
have important implications for alcoholism prevention and treatment to
the extent that study findings help us identify factors (a) that are
causally related to the development of alcoholism and (b) that lead to
improved risk assessment, improved predictability of course, improved
effectiveness in the application of intervention strategies, and
improved management of the chronicity of alcoholism disorders. |
Project
Five
Molecular Epidemiology of
Alcoholism and Comorbid Disorders
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| This new MARC research
project seeks to build upon gene-discovery projects such as
COGA (Collaborative Study on the Genetics of Alcoholism) and similar
projects which are
studying treatment-ascertained alcoholics and their relatives, and the
MARC-affiliated Alcohol-QTL IRPG consortium (PIs Heath, Martin, Madden,
Todd), which is studying community-ascertained alcoholics and heavy
smokers and their adult relatives, by incorporating a molecular genetic
component into 4 mature, prospective longitudinal studies spanning the
age-range from early adolescence into
young adulthood, with 3-7 waves of prospective assessment. In addition
to collecting DNA from the target samples (years 1-3), this research
project will combine secondary data-analysis and genotyping, proceeding
in 4 stages: (i) longitudinal and other phenotypic analyses to
establish consistent phenotype definition across informative data-sets
(not all data-sets will be informative for all phenotypes of interest)
(years 1-3); (ii) behavioral genetic analyses using existing twin data
sets (MOAFTS, the former MARC Project One, or other U.S. and Australian
data-sets to which we have access through the MARC) to confirm
heritability of phenotypes defined at stage (i), and where possible
determine whether that phenotypic operationalization is optimal for
understanding genetic effects (which may not be the case if the
structures of genetic and environmental influences are very different)
(years 1-3); (iii) genotyping for a limited number of candidate genes
(years 3-5); and (iv) genetic association analysis (years 4-5). This
carefully staged approach is necessary to minimize the dangers of
multiple testing when combining candidate gene data and rich
longitudinal data-sets. For the same reason, we focus on a limited
number of candidate phenotypes where prospective data are expected to
be informative for understanding the etiology of alcoholism, as
justified under Background and Preliminary studies. Selection of
candidate phenotypes and candidate genes is guided by the MARC focus on
the roles of overlapping mechanisms of behavioral undercontrol,
negative affect regulation and pharmacologic vulnerability in the
etiology of alcohol use disorders (AUDs), emphasizing AUD phenotypes
associated with (a) externalizing symptoms, (b) tolerance and
quantitative consumption indices, (c) cognitive aspects of alcohol use
(expectancies), (d) co-occurrence with tobacco dependence, and (e)
negataive affect (depression, suicidality). |
Project Six
Conjoint Alcohol and
Tobacco Use: An Ecological Study |
The comorbidity of alcohol
and tobacco use has been a central theme of ongoing MARC
investigations. Existing MARC-affiliated projects have used
epidemiological, behavior genetic, and laboratory methods to understand
the robust associations between drinking and smoking. Previously,
however,
the MARC research portfolio had not included studies that bridge the
basic laboratory research with the genetic epidemiology. Consequently,
relatively little is known about the motivational mechanisms that
contribute to the joint use of alcohol and tobacco in actual users
living in their natural environments. Using Ecological Momentary
Assessment (EMA; Stone & Shiffman, 1994) to investigate
hypothesized mechanisms that purportedly motivate joint use of alcohol
and cigarettes, we are prospectively assessing alcohol use and smoking,
their subjective antecedents and sequelae, and environmental contexts
in 400 smokers and 200 nonsmokers recruited from the community.
Electronic diary recording, which includes morning assessments,
drinking episode assessments, and smoking episode assessments, as well
as random prompts, occur over a 3-week period. This design will
permit within-subjects contrasts in the drinker-smokers that
characterize the unique motivational sequelae of joint drinking-smoking
moments relative to moments when only drinking, only smoking, or
neither are taking place. Additional comparisons between
drinker-smokers and drinkers only will be used to identify domains
where chronic effects of smoking (e.g., chronic cross-tolerance) or
other stable individual differences that differentiate smoking and
nonsmoking drinkers may contribute to the pattern of motivational
effects seen in drinker-smokers. Using hierarchical linear modeling,
and to a lesser extent, survival analysis, unique effects of conjoint
alcohol-smoking, relative to smoking alone and drinking alone, on both
positive and negative affective states will be explored, and the
relation between individual differences in conjoint alcohol-smoking and
substance-specific changes in positive/negative affect and subsequent
drinking and smoking behavior will be examined. Also, the extent to
which individual difference variables (e.g., sensation-seeking;
escapist motives for substance use) condition the magnitude of conjoint
and substance-specific effects on alcohol and/or tobacco seeking
behavior will be determined. In addition, the study will
determine the association between smoking level and acute and delayed
aversive (punishing) effects of alcohol, and will characterize the
extent to which individual differences in these aversive consequences
predict subsequent drinking behavior. |
Pilot Project 2
ADHD in Children of
Mothers Who Smoked During Pregnancy: Does the Effect Interact with
Paternal Alcoholism? |
In addition to the
evidence for substantial genetic effects on ADHD, there is increasing
evidence for the roles of parental alcoholism and maternal drinking and
smoking during pregnancy in the risk of offspring ADHD. Previous
studies have associated prenatal exposure to both alcohol and nicotine
with increased risk of ADHD in children. Preliminary analyses also
suggested (i) significant associations between parental alcoholism and
ADHD, as well as between maternal smoking during pregnancy and parental
alcoholism, and (ii) evidence for a genetic correlation between
parental alcoholism and offspring ADHD. Given these results, in
addition to genetic transmission, increased rates of maternal smoking
during pregnancy associated with parental alcoholism may be an
important factor contributing to the association between parental
alcoholism and ADHD. Taken together, evidence suggests that both
genetic and environmental risk factors for ADHD are at work in the
children of alcoholics, raising the possibility that these risk factors
may interact with one another. Using an innovative within-mother
comparison approach, this pilot study will assess relative effects of
maternal smoking during pregnancy on ADHD in 200 ‘high genetic risk’
children (100 sibling pairs with alcoholic fathers) and 200 ‘low
genetic risk’ children (100 sibling pairs with no history of paternal
alcoholism). The novel within-mother approach focuses on mothers who
have smoked during one pregnancy but not during all pregnancies,
allowing the comparison of outcomes between sibling pairs, one of which
has been exposed to nicotine prenatally and the other who has not,
while controlling for pertinent environmental variables (e.g., SES,
parental education, etc.). Thus, the samples are chosen for
environmental risk for ADHD from the maternal side (maternal smoking
during pregnancy) and genetic risk for ADHD from the paternal side
(those with history of DWI/alcohol problems). The sample will focus on
mothers who gave birth to children between 1992-1996 (children aged
7-11). A total of 4,835 mothers who are discordant for smoking during
their pregnancies have been identified from Missouri birth records. Of
these, 608 have a partner (listed as the father on the child's birth
record) who has been given a DWI. A total of 400 mothers will be
screened for eligibility (i.e., accuracy of birth records). Those
eligible to participate (200 projected) will be interviewed via
telephone regarding children’s ADHD, detailed smoking during pregnancy,
history of smoking and nicotine dependence, history of alcohol problems
and alcohol dependence, and limited parental psychopathology (i.e.,
screen for ADHD, screen for CD).
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Pilot Project 3
Genetic Epidemiology of
Alcohol and Tobacco Consumption in a Chinese Sample |
Alcohol and tobacco
consumption are a major public health problem. Twin and family studies
have suggested that both genetic and environmental risk factors are
associated with both behaviors and some genetic risk factors contribute
to the common risk of both behaviors. However, these results are found
in respondents with European ancestry. Lack of data from Asian
populations with different genetic and cultural background has limited
the generalizability of these findings. We propose a feasibility twin
study to examine the genetic and environmental contributions to alcohol
and tobacco consumption in a Chinese population as an initial step that
leads to the future large-scale replication twin study in China. We
will conduct a screening interview to assess zygosity and family
structure among 400 adult twins ascertained from the Qingdao Twin
Registry in China and blood drawing from a randomly selected sub-sample
of 82 twins and their twin siblings to confirm the accuracy of
self-reported zygosity. A diagnostic interview will be administered to
obtain a detail history of alcohol and tobacco smoking as well as
DSM-IV alcohol and nicotine dependence, major depression, anxiety
disorder and antisocial personality disorder in 200 twin pairs (50 MZ
and DZ male and 50 MZ and DZ female pairs). The screening interview
will be adapted from the Missouri Alcoholism Research Center (MARC)
projects. The Chinese CIDI will be used to derive the DSM-IV diagnoses.
The blood samples provided by the 50 of 82 twin pairs will also be used
for testing candidate genes including ADH2, ALDH2, and CYP2A6 genes.
The collection of twin data in this project represents an initial step
that leads to establishment of a Chinese twin registry, which will
allow us to conduct a large-scale cross-cultural genetic epidemiology
study. This pilot project will examine the following issues for alcohol
and tobacco consumption: (i) are genetic risks for alcohol or tobacco
consumption and dependence lower in the Chinese twin sample than twins
with European ancestry? (ii) is there evidence that alcohol and tobacco
consumption and dependence share genetic risks in this Chinese twin
sample as reported by other studies conducted in twins with European
ancestry? (iii) is there evidence that major depression and antisocial
personality disorder mediate or moderate genetic vulnerability to
alcohol and tobacco consumption and dependence in this Chinese twin
sample? (iv) is there evidence that ADH2, ALDH2, and CYP2A6 genes
contribute to the vulnerability to alcohol and tobacco use and
dependence after controlling for major depression, anxiety disorder and
antisocial personality disorder?
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